1. Field of the Invention
The present invention relates to image recording materials which may be used as planographic printing plate materials, color proofs, dry lith type film, photo resists, or color filters. More particularly, the present invention relates to image recording materials which can be used as planographic printing plate materials which allow direct plate making by manipulation of infrared laser beams based on digital signals from a computer, etc.
2. Description of the Related Art
Conventional apparatus for carrying out direct plate making from digital computer data include those making use of (1) electrophotography, (2) a photopolymerization system that uses a laser that emits blue or green light, (3) deposition of a silver salt on a light-sensitive resin, and (4) a silver salt diffusion transfer method.
However, apparatus employing (1) electrophotography is disadvantageous in that it requires intricate processes such as charging, exposure, and development for forming images, thus making the apparatus complex and large. An apparatus based on (2) photopolymerization involves use of a plate material which is highly sensitive to blue or green light, and therefore, such material cannot be easily handled in a lighted room. Methods (3) and (4) employ a silver salt, which has the drawbacks of requiring cumbersome processes for development, etc. and generating waste solution that contain silver.
Progress of laser technology in recent years has been amazing. Particularly with respect to solid-state lasers and semiconductor lasers that emit infrared rays having a wavelength of 760 nm-1200 nm, high output and compact laser devices have become readily available. Laser devices of these types are very useful as light sources for recording when direct plate making is performed through use of digital data from a computer, etc. However, since many photosensitive recording materials which are useful in practice are sensitive to wavelengths in the visible range of 760 nm or less, images cannot be recorded with these infrared laser devices. Therefore, there is need for materials capable of forming images with an infrared laser device.
As for image recording materials that can be used for recording with infrared laser devices, U.S. Pat. No. 4,708,925 discloses recording materials containing an onium salt, a phenol resin, and a spectral sensitizer. The recording materials disclosed in that patent permit recording not only with infrared lasers but also with UV rays or visible rays through varying the spectral sensitizer materials. These image recording materials are of the positive type and make use of the effect of the onium salt and phenol resin to inhibit dissolution into the developing solution. On the other hand, U.S. Pat. No. 5,372,907 discloses negative-type image recording materials containing an onium salt, a resol resin, a novolac resin, and an infrared absorber. These image recording materials are of the positive type when exposed to infrared laser rays or UV rays; however, after heat treatment following exposure, they provide negative images.
Plate materials for printing using the aforementioned image recording materials are problematic in that they tend to become smudged during printing. Moreover, with plate materials for printing using these image recording materials, film strength at image portions is insufficient, resulting in poor press life.